Did you ever figure the thrust washer dilemma out? It's been a couple of years, I tore into my 2002 Sierra and I do not have the thicker thrust washer & the lower with the two flanges was damaged inside my passenger side axle. I went to GM dealer today they told me that the flanged washer had a lot of problems so they have revised it to only 1 piece. Once I get the part from the dealer I will take a picture of it for future reference for everyone.